Glass laminated products for safety glass applications is characterized by high impact and penetration resistance, and does not scatter glass shards and debris when shattered. Glass laminates typically consists of a sandwich of two glass sheets or panels bonded together with an interlayer of a polymeric film or sheet, which is placed between the two glass sheets. One or both of the glass sheets may be replaced with optically clear rigid polymeric sheets, such as sheets of polycarbonate materials. Safety glass has further evolved to include multiple layers of glass sheets (or optically clear rigid polymeric sheets that are used in place of the glass) bonded together with interlayers of polymeric films or sheets.
The interlayer is typically made with a relatively thick polymer film or sheet, which exhibits toughness and bondability to provide adhesion to the glass in the event of a crack or crash. Over the years, a wide variety of polymeric interlayers have been developed to produce laminated products. In general, these polymeric interlayers must possess a combination of characteristics including very high optical clarity (low haze), high impact resistance, high penetration resistance, excellent ultraviolet light resistance, good long term thermal stability, excellent adhesion to glass and other rigid polymeric sheets, low ultraviolet light transmittance, low moisture absorption, high moisture resistance, excellent long term weatherability, among other requirements. Widely used interlayer materials utilized currently include complex, multicomponent compositions based on polyvinylbutyral (PVB), polyurethane (PU), polyvinylchloride (PVC), linear low density polyethylenes (preferably metallocene-catalyzed), ethylene vinyl acetate (EVAc), polymeric fatty acid polyamides, polyester resins, such as poly(ethylene terephthalate), silicone elastomers, epoxy resins, elastomeric polycarbonates, and the like.
A more recent trend has been the use of glass laminated products in the construction business for homes and office structures. The use of architectural glass has expanded rapidly over the years as designers incorporated more glass surfaces into buildings. Threat resistance has become an ever increasing requirement for architectural glass laminated products. These newer products are designed to resist both natural and man made disasters. Examples of these needs include the recent developments of hurricane resistant glass, now mandated in hurricane susceptible areas, theft resistant glazings, and the more recent blast resistant glass laminated products designed to protect buildings and their occupants. These products have great enough strength to resist intrusion even after the glass laminate has been broken, i.e., when a glass laminate is subjected to high force winds and impacts of flying debris as occur in a hurricane or where there are repeated impacts on a window by a criminal attempting to break into a vehicle or structure.
In addition, glass laminated products have now reached the strength requirements for being incorporated as structural elements within buildings. An example of this would be glass staircases now being featured in many buildings.
A part of this trend has been the use of copolyethylene ionomer resins as the glass laminate interlayer material. Such ionomer resins offer significantly higher strength then found for the other common interlayer materials, such as polyvinyl butyral and ethylene vinyl acetate materials. See, e.g., U.S. Pat. Nos. 3,344,014, 4,663,228, 4,668,574, 4,799,346, 5,002,820, 5,763,062, WO 99/58334 and WO 2004/011755.
Multilayer laminate constructions which include certain ionomeric materials have been disclosed within the art. Clock et al., U.S. Pat. No. 3,762,988, disclose a glass laminate multilayer interlayer which may include poly(ethylene-co-methacrylic acid) materials that have been neutralized with metal ions or amines as the core layer and a load distribution layer. Friedman et al., U.S. Pat. No. 6,432,522, disclose optically transparent glazings which include an interlayer film comprising at least two polymeric film layers; a core layer having a modulus of at least 25,000 psi, which may be an ionomeric material, and a surface film layer having a maximum modulus of 15,000 psi. Vogel et al., US 2002/0055006 and US 2005/0106386, disclose a multilayer film or sheet comprising: a) a first co-extruded polymeric layer consisting essentially of ionomer, and b) at least one co-extruded second polymeric layer selected from the group consisting of ionomer, ionomer-polyethylene blend and ionomer-polyamide blend.
Roberts et al., US 2005/0136263, discloses a flexible window comprising a transparent multilayer sheet comprising: a transparent flexible base layer formed of a substantially plasticizer free polymeric material which may include ionomers, and a first transparent flexible protective layer having a greater abrasion resistance than the transparent flexible base layer, said transparent multilayer sheet being sufficiently flexible to allow rolling it into a cylindrical shape without cracking or fracturing. Durbin et al., WO 01/60604, disclose a laminated glazing which includes a transparent flexible plastic which reflects infra-red radiation bonded between a ply of ionomer resin and a ply of a polymer material which has a higher viscosity than the ionomer layer.
Society continues to demand more functionality from laminated glass products beyond the safety and strength characteristics described above. One area of need is for the glass laminate to function as an acoustic barrier to reduce the level of noise intrusion into the structure that the glass laminate is attached to, such as a building or an automobile. Acoustic laminated glass is generally known within the art and generally is disclosed to include a low modulus, heavily plasticized poly(vinyl acetal) sheet, which suffers the shortcomings of providing laminates with a low penetration resistance. Acoustic laminate disclosures include, for example, U.S. Pat. Nos. 5,190,826, 5,340,654, 5,368,917, 5,464,659, 5,478,615, 5,773,102, 6,074,732, 6,119,807, 6,132,882, 6,432,522, 6,825,255, WO 01/19747 and WO 2004/039581.